lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

   1 //===-- RuntimeDyldELF.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Implementation of ELF support for the MC-JIT runtime dynamic linker.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "dyld"
  15 #include "llvm/ADT/OwningPtr.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/ADT/STLExtras.h"
  18 #include "llvm/ADT/IntervalMap.h"
  19 #include "RuntimeDyldELF.h"
  20 #include "llvm/Object/ObjectFile.h"
  21 #include "llvm/Support/ELF.h"
  22 #include "llvm/ADT/Triple.h"
  23 #include "llvm/Object/ELF.h"
  24 #include "JITRegistrar.h"
  25 using namespace llvm;
  26 using namespace llvm::object;
  27
  28 namespace {
  29
  30 template<support::endianness target_endianness, bool is64Bits>
  31 class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
  32   LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
  33
  34   typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
  35   typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
  36   typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
  37   typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
  38
  39   typedef typename ELFObjectFile<target_endianness, is64Bits>::
  40     Elf_Ehdr Elf_Ehdr;
  41
  42   typedef typename ELFDataTypeTypedefHelper<
  43           target_endianness, is64Bits>::value_type addr_type;
  44
  45 protected:
  46   // This duplicates the 'Data' member in the 'Binary' base class
  47   // but it is necessary to workaround a bug in gcc 4.2
  48   MemoryBuffer *InputData;
  49
  50 public:
  51   DyldELFObject(MemoryBuffer *Object, error_code &ec);
  52
  53   void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
  54   void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
  55
  56   const MemoryBuffer& getBuffer() const { return *InputData; }
  57
  58   // Methods for type inquiry through isa, cast and dyn_cast
  59   static inline bool classof(const Binary *v) {
  60     return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
  61             && classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
  62   }
  63   static inline bool classof(
  64       const ELFObjectFile<target_endianness, is64Bits> *v) {
  65     return v->isDyldType();
  66   }
  67   static inline bool classof(const DyldELFObject *v) {
  68     return true;
  69   }
  70 };
  71
  72 template<support::endianness target_endianness, bool is64Bits>
  73 class ELFObjectImage : public ObjectImage {
  74   protected:
  75     DyldELFObject<target_endianness, is64Bits> *DyldObj;
  76     bool Registered;
  77
  78   public:
  79     ELFObjectImage(DyldELFObject<target_endianness, is64Bits> *Obj)
  80     : ObjectImage(Obj),
  81       DyldObj(Obj),
  82       Registered(false) {}
  83
  84     virtual ~ELFObjectImage() {
  85       if (Registered)
  86         deregisterWithDebugger();
  87     }
  88
  89     // Subclasses can override these methods to update the image with loaded
  90     // addresses for sections and common symbols
  91     virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
  92     {
  93       DyldObj->updateSectionAddress(Sec, Addr);
  94     }
  95
  96     virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
  97     {
  98       DyldObj->updateSymbolAddress(Sym, Addr);
  99     }
 100
 101     virtual void registerWithDebugger()
 102     {
 103       JITRegistrar::getGDBRegistrar().registerObject(DyldObj->getBuffer());
 104       Registered = true;
 105     }
 106     virtual void deregisterWithDebugger()
 107     {
 108       JITRegistrar::getGDBRegistrar().deregisterObject(DyldObj->getBuffer());
 109     }
 110 };
 111
 112 template<support::endianness target_endianness, bool is64Bits>
 113 DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Object,
 114                                                           error_code &ec)
 115   : ELFObjectFile<target_endianness, is64Bits>(Object, ec),
 116     InputData(Object) {
 117   this->isDyldELFObject = true;
 118 }
 119
 120 template<support::endianness target_endianness, bool is64Bits>
 121 void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
 122                                                        const SectionRef &Sec,
 123                                                        uint64_t Addr) {
 124   DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
 125   Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
 126                           reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
 127
 128   // This assumes the address passed in matches the target address bitness
 129   // The template-based type cast handles everything else.
 130   shdr->sh_addr = static_cast<addr_type>(Addr);
 131 }
 132
 133 template<support::endianness target_endianness, bool is64Bits>
 134 void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
 135                                                        const SymbolRef &SymRef,
 136                                                        uint64_t Addr) {
 137
 138   Elf_Sym *sym = const_cast<Elf_Sym*>(
 139                                  ELFObjectFile<target_endianness, is64Bits>::
 140                                    getSymbol(SymRef.getRawDataRefImpl()));
 141
 142   // This assumes the address passed in matches the target address bitness
 143   // The template-based type cast handles everything else.
 144   sym->st_value = static_cast<addr_type>(Addr);
 145 }
 146
 147 } // namespace
 148
 149
 150 namespace llvm {
 151
 152 ObjectImage *RuntimeDyldELF::createObjectImage(
 153                                          const MemoryBuffer *ConstInputBuffer) {
 154   MemoryBuffer *InputBuffer = const_cast<MemoryBuffer*>(ConstInputBuffer);
 155   std::pair<unsigned char, unsigned char> Ident = getElfArchType(InputBuffer);
 156   error_code ec;
 157
 158   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
 159     DyldELFObject<support::little, false> *Obj =
 160            new DyldELFObject<support::little, false>(InputBuffer, ec);
 161     return new ELFObjectImage<support::little, false>(Obj);
 162   }
 163   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
 164     DyldELFObject<support::big, false> *Obj =
 165            new DyldELFObject<support::big, false>(InputBuffer, ec);
 166     return new ELFObjectImage<support::big, false>(Obj);
 167   }
 168   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
 169     DyldELFObject<support::big, true> *Obj =
 170            new DyldELFObject<support::big, true>(InputBuffer, ec);
 171     return new ELFObjectImage<support::big, true>(Obj);
 172   }
 173   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
 174     DyldELFObject<support::little, true> *Obj =
 175            new DyldELFObject<support::little, true>(InputBuffer, ec);
 176     return new ELFObjectImage<support::little, true>(Obj);
 177   }
 178   else
 179     llvm_unreachable("Unexpected ELF format");
 180 }
 181
 182 void RuntimeDyldELF::handleObjectLoaded(ObjectImage *Obj)
 183 {
 184   Obj->registerWithDebugger();
 185   // Save the loaded object.  It will deregister itself when deleted
 186   LoadedObject = Obj;
 187 }
 188
 189 RuntimeDyldELF::~RuntimeDyldELF() {
 190   if (LoadedObject)
 191     delete LoadedObject;
 192 }
 193
 194 void RuntimeDyldELF::resolveX86_64Relocation(uint8_t *LocalAddress,
 195                                              uint64_t FinalAddress,
 196                                              uint64_t Value,
 197                                              uint32_t Type,
 198                                              int64_t Addend) {
 199   switch (Type) {
 200   default:
 201     llvm_unreachable("Relocation type not implemented yet!");
 202   break;
 203   case ELF::R_X86_64_64: {
 204     uint64_t *Target = (uint64_t*)(LocalAddress);
 205     *Target = Value + Addend;
 206     break;
 207   }
 208   case ELF::R_X86_64_32:
 209   case ELF::R_X86_64_32S: {
 210     Value += Addend;
 211     // FIXME: Handle the possibility of this assertion failing
 212     assert((Type == ELF::R_X86_64_32 && !(Value & 0xFFFFFFFF00000000ULL)) ||
 213            (Type == ELF::R_X86_64_32S &&
 214             (Value & 0xFFFFFFFF00000000ULL) == 0xFFFFFFFF00000000ULL));
 215     uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
 216     uint32_t *Target = reinterpret_cast<uint32_t*>(LocalAddress);
 217     *Target = TruncatedAddr;
 218     break;
 219   }
 220   case ELF::R_X86_64_PC32: {
 221     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 222     int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 223     assert(RealOffset <= 214783647 && RealOffset >= -214783648);
 224     int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
 225     *Placeholder = TruncOffset;
 226     break;
 227   }
 228   }
 229 }
 230
 231 void RuntimeDyldELF::resolveX86Relocation(uint8_t *LocalAddress,
 232                                           uint32_t FinalAddress,
 233                                           uint32_t Value,
 234                                           uint32_t Type,
 235                                           int32_t Addend) {
 236   switch (Type) {
 237   case ELF::R_386_32: {
 238     uint32_t *Target = (uint32_t*)(LocalAddress);
 239     uint32_t Placeholder = *Target;
 240     *Target = Placeholder + Value + Addend;
 241     break;
 242   }
 243   case ELF::R_386_PC32: {
 244     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 245     uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 246     *Placeholder = RealOffset;
 247     break;
 248     }
 249     default:
 250       // There are other relocation types, but it appears these are the
 251       //  only ones currently used by the LLVM ELF object writer
 252       llvm_unreachable("Relocation type not implemented yet!");
 253       break;
 254   }
 255 }
 256
 257 void RuntimeDyldELF::resolveARMRelocation(uint8_t *LocalAddress,
 258                                           uint32_t FinalAddress,
 259                                           uint32_t Value,
 260                                           uint32_t Type,
 261                                           int32_t Addend) {
 262   // TODO: Add Thumb relocations.
 263   uint32_t* TargetPtr = (uint32_t*)LocalAddress;
 264   Value += Addend;
 265
 266   DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: " << LocalAddress
 267                << " FinalAddress: " << format("%p",FinalAddress)
 268                << " Value: " << format("%x",Value)
 269                << " Type: " << format("%x",Type)
 270                << " Addend: " << format("%x",Addend)
 271                << "\n");
 272
 273   switch(Type) {
 274   default:
 275     llvm_unreachable("Not implemented relocation type!");
 276
 277   // Just write 32bit value to relocation address
 278   case ELF::R_ARM_ABS32 :
 279     *TargetPtr = Value;
 280     break;
 281
 282   // Write first 16 bit of 32 bit value to the mov instruction.
 283   // Last 4 bit should be shifted.
 284   case ELF::R_ARM_MOVW_ABS_NC :
 285     Value = Value & 0xFFFF;
 286     *TargetPtr |= Value & 0xFFF;
 287     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 288     break;
 289
 290   // Write last 16 bit of 32 bit value to the mov instruction.
 291   // Last 4 bit should be shifted.
 292   case ELF::R_ARM_MOVT_ABS :
 293     Value = (Value >> 16) & 0xFFFF;
 294     *TargetPtr |= Value & 0xFFF;
 295     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 296     break;
 297
 298   // Write 24 bit relative value to the branch instruction.
 299   case ELF::R_ARM_PC24 :    // Fall through.
 300   case ELF::R_ARM_CALL :    // Fall through.
 301   case ELF::R_ARM_JUMP24 :
 302     int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
 303     RelValue = (RelValue & 0x03FFFFFC) >> 2;
 304     *TargetPtr &= 0xFF000000;
 305     *TargetPtr |= RelValue;
 306     break;
 307   }
 308 }
 309
 310 void RuntimeDyldELF::resolveRelocation(uint8_t *LocalAddress,
 311                                        uint64_t FinalAddress,
 312                                        uint64_t Value,
 313                                        uint32_t Type,
 314                                        int64_t Addend) {
 315   switch (Arch) {
 316   case Triple::x86_64:
 317     resolveX86_64Relocation(LocalAddress, FinalAddress, Value, Type, Addend);
 318     break;
 319   case Triple::x86:
 320     resolveX86Relocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 321                          (uint32_t)(Value & 0xffffffffL), Type,
 322                          (uint32_t)(Addend & 0xffffffffL));
 323     break;
 324   case Triple::arm:    // Fall through.
 325   case Triple::thumb:
 326     resolveARMRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 327                          (uint32_t)(Value & 0xffffffffL), Type,
 328                          (uint32_t)(Addend & 0xffffffffL));
 329     break;
 330   default: llvm_unreachable("Unsupported CPU type!");
 331   }
 332 }
 333
 334 void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
 335                                           ObjectImage &Obj,
 336                                           ObjSectionToIDMap &ObjSectionToID,
 337                                           const SymbolTableMap &Symbols,
 338                                           StubMap &Stubs) {
 339
 340   uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
 341   intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
 342   const SymbolRef &Symbol = Rel.Symbol;
 343
 344   // Obtain the symbol name which is referenced in the relocation
 345   StringRef TargetName;
 346   Symbol.getName(TargetName);
 347   DEBUG(dbgs() << "\t\tRelType: " << RelType
 348                << " Addend: " << Addend
 349                << " TargetName: " << TargetName
 350                << "\n");
 351   RelocationValueRef Value;
 352   // First search for the symbol in the local symbol table
 353   SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
 354   if (lsi != Symbols.end()) {
 355     Value.SectionID = lsi->second.first;
 356     Value.Addend = lsi->second.second;
 357   } else {
 358     // Search for the symbol in the global symbol table
 359     SymbolTableMap::const_iterator gsi =
 360         GlobalSymbolTable.find(TargetName.data());
 361     if (gsi != GlobalSymbolTable.end()) {
 362       Value.SectionID = gsi->second.first;
 363       Value.Addend = gsi->second.second;
 364     } else {
 365       SymbolRef::Type SymType;
 366       Symbol.getType(SymType);
 367       switch (SymType) {
 368         case SymbolRef::ST_Debug: {
 369           // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
 370           // and can be changed by another developers. Maybe best way is add
 371           // a new symbol type ST_Section to SymbolRef and use it.
 372           section_iterator si(Obj.end_sections());
 373           Symbol.getSection(si);
 374           if (si == Obj.end_sections())
 375             llvm_unreachable("Symbol section not found, bad object file format!");
 376           DEBUG(dbgs() << "\t\tThis is section symbol\n");
 377           Value.SectionID = findOrEmitSection(Obj, (*si), true, ObjSectionToID);
 378           Value.Addend = Addend;
 379           break;
 380         }
 381         case SymbolRef::ST_Unknown: {
 382           Value.SymbolName = TargetName.data();
 383           Value.Addend = Addend;
 384           break;
 385         }
 386         default:
 387           llvm_unreachable("Unresolved symbol type!");
 388           break;
 389       }
 390     }
 391   }
 392   DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
 393                << " Rel.Offset: " << Rel.Offset
 394                << "\n");
 395   if (Arch == Triple::arm &&
 396       (RelType == ELF::R_ARM_PC24 ||
 397        RelType == ELF::R_ARM_CALL ||
 398        RelType == ELF::R_ARM_JUMP24)) {
 399     // This is an ARM branch relocation, need to use a stub function.
 400     DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
 401     SectionEntry &Section = Sections[Rel.SectionID];
 402     uint8_t *Target = Section.Address + Rel.Offset;
 403
 404     //  Look up for existing stub.
 405     StubMap::const_iterator i = Stubs.find(Value);
 406     if (i != Stubs.end()) {
 407       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 408                         i->second, RelType, 0);
 409       DEBUG(dbgs() << " Stub function found\n");
 410     } else {
 411       // Create a new stub function.
 412       DEBUG(dbgs() << " Create a new stub function\n");
 413       Stubs[Value] = Section.StubOffset;
 414       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 415                                                    Section.StubOffset);
 416       RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
 417                          ELF::R_ARM_ABS32, Value.Addend);
 418       if (Value.SymbolName)
 419         addRelocationForSymbol(RE, Value.SymbolName);
 420       else
 421         addRelocationForSection(RE, Value.SectionID);
 422
 423       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 424                         Section.StubOffset, RelType, 0);
 425       Section.StubOffset += getMaxStubSize();
 426     }
 427   } else {
 428     RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 429     if (Value.SymbolName)
 430       addRelocationForSymbol(RE, Value.SymbolName);
 431     else
 432       addRelocationForSection(RE, Value.SectionID);
 433   }
 434 }
 435
 436 bool RuntimeDyldELF::isCompatibleFormat(const MemoryBuffer *InputBuffer) const {
 437   StringRef Magic = InputBuffer->getBuffer().slice(0, ELF::EI_NIDENT);
 438   return (memcmp(Magic.data(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
 439 }
 440 } // namespace llvm